Many existing and future broadband satellite services require small, lightweight and low-cost antennas to be mounted on mobile platforms, such as vehicles, trains, and airplanes, or antennas integrated on portable systems or installed in fixed positions on buildings. In order to minimize the size and/or the thickness of the antenna and to provide beam steering capabilities, array antennas are often applied for wall-mount applications, portable applications and mobile front-end applications.
Satellite services with large capacity and fast connection speed often apply high frequency bands (e.g. Ku, Ka and Q-band) which typically have large frequency ranges for downlink and uplink channels. These services also typically have large spacing between transmit and receive bands in order to avoid interferences between uplink and downlink signals. The large bandwidths and the large spacing between bands make it difficult to design antenna arrays using the same aperture for both uplink and downlink functions. One solution used in many products is to split the antenna aperture in two parts, one aperture for receiving signals and another aperture for transmitting signals.
An advantageous approach is to use the same surface and volume of the antenna for both transmit and receive functionalities. This is generally achieved in reflector antennas through the design of wideband feeds which integrate diplexers to separate transmit and receive signals. However, using the same surface is difficult in array antennas where wideband elements tend to loose radiation efficiency in the required bands and where the integration of active components (e.g. for beam steering) includes a separation of transmit and receive signals at each element, generally resulting in an increase in costs and integration issues.
Additionally, integrating two types of elements, one for transmit and one for receive, in the same surface, may result in a high coupling between elements that affects quality of the radiation of the antenna. Typically, the antenna design is very challenging because the spacing between radiating elements is very small and field couplings very high. The high couplings between the two types of elements can cause problems on the generation of the beam forming and power isolation between the transmit and receive chain. Overall, designing the receive function and the transmit function onto a single aperture may result in inefficiencies, increased complexity and cost, and high coupling between the radiating elements.
Thus, it is desirable to have an antenna architecture having both transmit and receive elements on a single aperture, and where the antenna architecture is configured to operate efficiently and with reduced coupling between the elements.